Directional cell migration is important in many physiological and pathological processes including embryonic development, wound healing, angiogenesis, tumour invasion and metastasis. Transduction of extracellular signals, that stimulate cells to move directionally, may be induced by a number of processes including trans-membrane integrins binding to extra cellular matrix proteins and the action of growth factors (for example EGF, IGF and VEGF) on the extracellular domains of their cognate receptors.
FAK is a non receptor tyrosine kinase that mediates signals from both trans-membrane integrins and growth factor receptors. FAK has been reported to play a central role in coordinating these diverse extra cellular signals, integrating them in a fashion that results in directional movement of cells through their external environment (Tomar and Schlaepfer. Current Opinion in Cell Biology: 2009, 21, 676-683).
Integrin clustering or the activation of a growth factor receptor (for example EGFR, IGF-1R, Her2 and VEGFR) promotes FAK autophosphorylation at Y397. Phosphorylated Y397 FAK then binds to c-Src (referred to as Src herein) and Src mediated phosphorylation of FAK at Y576 and Y577 occurs to give rise to an active FAK-Src complex. Active FAK-Src then facilitates signaling via a number of biochemical pathways which influence processes such as cell adhesion, migration, invasion, cell survival, proliferation, acquisition of chemotherapy resistance and metastasis (Brunton and Frame. Current Opinion in Pharmacology: 2008, 8, 437-432 and Chatzizacharias et al. Expert Opinion in Therapeutic Targets: 2007, 11(10), 1315-1328).
Cell Adhesion
Functional studies addressing the role of FAK in cell adhesion suggest that it contributes to both focal adhesion assembly (Richardson and Parsons. Nature: 1996, 380, 538-540) and focal adhesion turnover (Fincham et al. Oncogene: 1995, 10(11), 2247-2252). Inhibition of FAK by RNAi in both human and mouse cell lines, resulting in decreased FAK protein levels, has been shown to reduce cell adhesion to a fibronectin/laminin-coated plate in vitro (Tsutsumi et al. International Journal of Oncology: 2008, 33(1), 215-224).
Cell Migration
There is strong evidence that FAK is a key regulator of cell migration (Angelucci and Bologna. Current Pharmaceutical Design: 2007, 13, 2129-2145 and Mitra et al. Nature Reviews Molecular Cell Biology: 2005, 6, 56-68). Cells derived from FAK −/− mouse embryos exhibit reduced migration as a result of impaired adhesion turnover (llić et al. Nature: 1995, 377, 539-544). Moreover, displacement of FAK from focal adhesions reduces cell migration (Gilmore and Romer. Molecular Biology of the Cell: 1996, 7(8), 1209-1224), whilst over-expression in CHO cells stimulates migration (Cary et al. Journal of Cell Science: 1996, 7, 1787-1794). In addition, inhibition of FAK by RNAi in both human and mouse cell lines, resulting in decreased FAK protein levels, has been shown to reduce cell migration in an in vitro haptotactic migration assay (Tsutsumi et al. International Journal of Oncology: 2008, 33(1), 215-224).
Cell Invasion
FAK activation has been shown to enhance matrix degrading invasive behaviour. FAK-Src signaling through cellular apoptosis susceptibility protein (CAS) (Liao et al. Journal of Experimental and Clinical Cancer Research: 2008, 27:15) leads to the expression of matrix metalloproteases (MMPs) including MMP2 and MMP9. FAK-Src activation also promotes cell surface expression of MMP14 via phosphorylation of endophilin A2. MMP14 then activates MMP2 by cleavage of pro-MMP2 to its active form (Siesser and Hanks. Clinical Cancer Research: 2006, 12(11), 3233-3237). Highly invasive cancer cells form specialized actin-rich extra cellular matrix degrading membrane protrusions known as invadopodia which are rich in matrix-degrading proteases such as MMPs. Both FAK and Src have been shown to be instrumental in the formation of invadopodia (Chan et al. Journal of Chemical Biology: 2009, 185(2), 357-370).
Cell Survival
FAK has been shown to play an important role in cell survival. Activation of FAK has been shown to result in suppression of anoikis (apopotosis in response to an inappropriate extra cellular matrix environment) (Frisch et al Journal of Cell Biology. 1996, 134(3), 793-799 and Xu et al Cell Growth and Differentiation. 1996, 7(4), 413-418). Studies have demonstrated that FAK activates multiple downstream pathways to suppress anoikis in both fibroblasts and epithelial cells (Zouq et al. Journal of Cell Science: 2008, 122, 357-367). In human intestinal crypt cells signalling via the association of FAK with β1 integrin and subsequent binding with Src up regulates expression of the anti-apoptotic proteins Bcl-XL and Mcl-1 via PI3-K/Akt-1 signalling. PI3-K/Akt-1 signalling also down regulates expression of the pro-apoptotic activators Bax and Bak, causes phosphorylation of the pro-apoptotic sensitizer Bad and antagonizes p38β activation. Dissociation of FAK/Src results in a sustained/enhanced activation of p38β which is an apoptosis/anoikis driver (Bouchard et al. Apoptosis: 2008, 13, 531-542).
Cell Proliferation
Reduction in the expression of either FAK or β1 integrin and hence disruption of the β1-FAK signalling axis results in decreased initial proliferation of micro-metastatic cells distributed in the lung. Using 3D cultured D2 cells a strong correlation was observed between FAK Y397 and Y861 phosphorylation and proliferative ability (Shibue and Weinberg. PNAS 2009, 106(25), 10290-10295). HL-60 Cells, transfected to over express FAK, have been shown to double at a rate 1.5 times faster than control HL-60 cells. Studies revealed a marked induction of cyclin D3 expression and CDK activity in the cells over expressing FAK. Activation of PI3-K/Akt-1 signalling, a process associated with FAK activation in a number of studies, was identified as a probable cause of the cyclin expression/activation (Yamamoto et al. Cellular Signaling: 2003, 15. 575-583).
Acquisition of Chemotherapy Resistance
Exposure of the cisplatin sensitive ovarian cancer cell line OAW42 to repeated cycles of cisplatin treatment and subsequent recovery resulted in the formation of chemo-resistant OAW42-R cells. Studies aimed at identifying the cause of this chemo-resistance revealed that FAK was constituently active in both the sensitive and chemo-resistant cells. However, inhibition of phosphorylation of Y397 FAK was induced by treatment with cisplatin in OAW42 cells but not in OAW42-R cells (Poulain and co-workers. Gynaecologic oncology: 2006, 101, 507-519). The effects of FAK inhibition on chemo-resistance has also been studied in vitro and in vivo using the FAK inhibitor TAE226, alone and in combination with docetaxel, in taxane-sensitive (SKOV3ip1 and HeyA8) and taxane-resistant (HeyA8-MDR) ovarian cancer cell lines. TAE226 has the structure:
and is described in WO 2004/080980 and WO 2005/016894. In vitro, TAE226 inhibited the phosphorylation of FAK at both Y397 and Y861 sites, inhibited cell growth in a time- and dose-dependent manner, and enhanced docetaxel-mediated growth inhibition by 10- and 20-fold in the taxane-sensitive and taxane-resistant cell lines, respectively. In vivo, FAK inhibition by TAE226 significantly reduced tumour burden in the HeyA8, SKOV3ip1, and HeyA8-MDR models (46-64%) compared with vehicle-treated controls. However, the greatest efficacy was observed with concomitant administration of TAE226 and docetaxel in all three models (85-97% reduction). In addition, TAE226 in combination with docetaxel significantly prolonged survival in tumour-bearing mice (Halder et al. Cancer Res: 2007, 67(22), 10976-10983).Metastatic Potential
Several studies have examined the role of FAK protein levels and it's relation to tumor progression in animal models. In a mouse skin carcinogenesis model using FAK +/− mice, reduced FAK protein expression correlated with decreased papilloma formation (46%), compared with FAK +/+ wild-type control mice (McLean et al. Cancer Research: 2001, 61, 8385-8389). Using human breast carcinoma cells, researchers showed that FAK siRNA treated cells were inhibited from metastasizing to the lung after orthotopic implantation in nude mice (Benlimame et al. Journal of Cell Biology: 2005, 171, 505-516). Similar experiments using short hairpin RNA (shRNA) against FAK in 4T1 mouse breast carcinoma cells resulted in an inhibition of metastasis to the lungs after orthotopic implantation in mammary pads (Mitra et al. Oncogene: 2006, 25, 4429-4440). Inhibition of FAK by dominant negative expression in 4T1 mouse breast carcinoma cells reduced tumour growth and angiogenesis in mice (Mitra et al. Oncogene: 2006, 25, 5969-5984). Use of a Cre/loxP recombination system to disrupt FAK function in the mammary epithelium of a transgenic model of breast cancer has demonstrated that FAK expression is required for the transition of premalignant hyperplasias to carcinomas and their subsequent metastases. The observed decrease in tumor progression was further correlated with impaired mammary epithelial proliferation suggesting that FAK plays a critical role in mammary tumor progression (Lahlou et al. PNAS USA: 2007, 104(51), 20302-20307).
In accordance with the above observations over expression of FAK mRNA and/or protein has been reported in numerous human cancers including colorectal cancer (de Heer. European Journal of Surgical Oncology: 2008, 34(11), 1253-1261), prostate cancer (Tremblay, L., W. Hauck, et al. International Journal of Cancer: 1996, 68(2), 164-171), breast cancer (Watermann et al. British Journal of Cancer 2005, 93(6), 694-698) and melanomas (Hess et al. Cancer Research: 2005, 65(21), 9851-60). Furthermore FAK over expression is frequently correlated with more aggressive phenotypes of these cancers.
Thus, there is strong evidence to suggest that a FAK inhibitor would have application for the reduction of cell adhesion, cell migration, cell invasion, cell proliferation and chemo-resistance. Furthermore, a FAK inhibitor would have applicability to induce apoptosis for cells in inappropriate extra cellular matrix environments and reduce angiogenesis.
It will be appreciated that activity at other tyrosine kinases and serine/threonine kinase in combination with FAK activity may be beneficial for the treatment of proliferative diseases, such as cancer.
For example, the vascular endothelial growth factor receptor VEGFR3 (Flt4) is over expressed in melanoma patients with metastases in regional lymph nodes (Mouawad et al. European Journal of Cancer: 2009, 45, 1407-1414). Abnormal expression levels of endogenous receptor tyrosine kinase ligands are also observed in many human cancers. For example, the expression levels of vascular endothelial growth factors C and D (VEGF-C and VEGF-D), ligands of VEGFR3, are significantly correlated with lymphatic metastasis and lymphatic vessel invasion in early-stage invasive cervical carcinoma (Journal of Experimental & Clinical Cancer Research 2009, 28).
Accordingly, compounds that selectively inhibit FAK and VEGFR3 would be useful for the treatment of proliferative diseases, such as cancer.
Two compounds reported to inhibit FAK are PF-562,271 and PF-573,228.

PF-562,271 is described in WO2004/056786, WO2004/056807, WO2005/023780, WO2007/063384 and Roberts et al. Cancer Res 2008, 68(6), 1935-1944.
PF-573,228 is described in Slack-Davis et al. J. Biol. Chem. 2007, 282(20), 14845-14852.
In addition to these specifically described compounds, further classes of FAK inhibitors are disclosed in WO2008/129380, WO2008/115369, WO2009/105498, US2010/113475, WO2009/143389, WO2009/071535, WO2010/055117, WO2010/058030, WO2010/058032, WO2007/140222, and WO2009/024332.